Before I would go so far as to give you advice like this, I would want to get a good visual on both the parents. I understand if you want to do this privately.
I have so far, been able to "see" dwarf traits in almost every horse that has produced one, if not in both parents, at least in one of them. there are many traits that others call "acceptable" and I myself don't. I had a little filly here with three of my "unacceptable" traits and as if one of them (an underbite) wasn't enough, the heavy bone for her height and high dome on her forehead (not placed low between the eyes, it was closer to her ears) made me come to the conclusion that she carried a dwarf gene, and could pass it. I had people tell me they thought she was fine, but just telling you my decision. She is now a happy, loved pet.
I am a very small breeder as in I only have two mares that are breeding age, and often have just one foal per year. I can't afford to "play around" with things that make me suspicious.
I've had minis for 12 years now, and before that, I had friends that had them, and so my experience in observing them and some of the dwarf births in a few larger herds (as well as smaller ones), goes back to about 1990. Even though I didn't know "minis" per se, I knew horses, and I could see the flawed conformation which seemed to be indicative of what had come together to make these dwarfs. I was a bit surprised in a few cases, but most times, the proportions are off just enough (and not uniformly) that a dwarf is not a complete surprise.
So if you'd like to send photos of both the parents of the dwarf baby as well as the new sire, I would give you my opinion on whether to breed them or not. Myself, I would tend not to just because I do have a very small operation, and even if it were my most favorite and best-bred mare, I would tend to want to "not" breed her again, to anyone.
[email protected] is my email or you can send links to pics to my PM.
(pointing out that I am not a genetic scientist, none of my observations or opinions are based on anything but my knowledge of horse conformation as well as an "average" for Miniature proportions and conformation. I have no scientific proof to back up any of my observations, and I also don't make money breeding Miniatures. Probably never will, so my decisions are not based on any financial need nor competition in the market, they are more directly as a result of concern for the breed as well as my own horse's well-being)
Liz M.